A single three-hour stay and mindfulness, emotions and heart rate variability

In one sentence

After three hours, both the stay in darkness and silence and the stay in an ordinary room lowered anxiety and raised HRV; the groups differed in mindfulness — Chamber-REST participants showed clearly more curiosity towards their own experience and more distance from it.

The researchers' question

Does a single three-hour Chamber-REST session evoke a mindful state and change emotions and physiological regulation in young adults — and does the response depend on resting heart rate variability (HRV), a marker of self-regulation capacity and stress resilience?

The authors point to young adults as a group particularly exposed to stress, smartphone dependence and digital immersion, and short of time for self-reflection.

Who took part

• 191 students from a non-clinical population (mean age 22.4, 66% women): 130 in Chamber-REST, 61 in the control group.
• Exclusions: cardiovascular, psychiatric and neurological disorders, psychotropic medication, BMI below 18.5 or above 25.
• Nearly 4 in 5 participants used a smartphone at least 3 hours a day; 55.5% had regular meditation experience.
• The groups were matched 1:1 (including sex, age, smartphone use, sport, FoMO, anxiety and HRV before the study) — the comparison covered 58 + 58 people.
• The study group was split at the HRV median into high and low HRV groups of 65 each.

Procedure

• At least 2 days before: written instructions with photos of the room and procedure, including safety aspects. Participation was voluntary; participants decided how long to take to get used to the setting.
• On site: about 10 minutes of habituation in full light, a 5-minute seated HRV recording, state questionnaires.
• 3 hours of Chamber-REST in the same laboratory as the stress study. A phone could be used only as an alarm, wrapped in a blanket so no light escaped. Participants were not told how much time had passed.
• After the stay: another HRV recording and questionnaires, including the mindfulness scale and satisfaction with the stay.
• Control group: as in the stress study — a bright room, everyday activities, phone; no sleeping, closed eyes or meditation.

What was measured

• HRV — the RMSSD index, linked to parasympathetic activity; 5-minute ECG recording before and after.
• State anxiety — STAI.
• Feeling stressed, calm, tired and aroused — the SACL adjective checklist.
• State mindfulness — Toronto Mindfulness Scale: curiosity and decentering (distance from one's own experience); after the stay only.
• Traits: FoMO, smartphone use, sport, meditation experience.

Results: both groups

• State anxiety fell in both groups (Chamber-REST 44.8 → 37.1; control 44.5 → 38.3) and HRV rose — with a larger effect in the control group.
• Feeling stressed fell and feeling calm rose in both groups — with a larger effect in the Chamber-REST group. Fatigue fell only in the Chamber-REST group.
• After the stay, the groups did not differ significantly in anxiety, HRV, stress, calm, fatigue or satisfaction (7.9 out of 10 in both).

Results: mindfulness and HRV

• The groups differed in mindfulness: curiosity 15.7 vs 8.3 (large effect, r = 0.59), decentering 14.2 vs 9.7 (medium to large effect, r = 0.42).
• Mindfulness scores did not differ between meditators and non-meditators, nor between HRV groups.
• Low HRV: parasympathetic activity rose in 94% of people (high HRV: 63%). Anxiety fell in a similar share of both groups (83% and 80%).
• Only in the low HRV group did decentering predict feeling calm after the session — explaining 23% of its variance.
• Before the stay, HRV was linked to feeling stressed and calm only in the low HRV group — the authors relate this to stronger anticipation of a new, unfamiliar situation.

What was not shown

The hypotheses were partly confirmed: the stay gave no advantage over the control group in anxiety, HRV or satisfaction. The authors conclude that Chamber-REST may matter more for psychological outcomes than for immediate physiological responses — as in their earlier cortisol study, which also found no difference.

How the authors explain it

Unlike mindfulness training, where participants are given instructions, Chamber-REST offers an unstructured environment free of distractions — self-reflection arises spontaneously. Decentering lets people view their own reactions from an observer's position, and curiosity lets them approach those reactions openly. Both may support a better understanding of one's own coping patterns.

Limitations

• Non-random assignment and separate recruitment of the control group.
• State mindfulness was measured only after the stay — a group comparison, not change over time.
• Differences in body position and movement during the stay may have affected HRV — the authors note this.
• First contact with the procedure: anticipating a new situation may have affected baseline HRV.
• A selected group of healthy students; the exclusion criteria are not a list of contraindications for other people.

The authors' figures and tables — in the original

Because of the licence, the figures are not reproduced on this site. Each is available in the full text:

• Table 1 ↗ — Comparison of the matched groups before and after — the data source of our charts.
• Table 2 ↗ — Before–after changes in both groups (Friedman test).
• Table 6 ↗ — Number of people with positive and negative responses in the high and low HRV groups.
• Fig. 1 ↗ — Relationship between decentering and calm after the session in the low HRV group.